Issue 31

E.M. Nurullaev et alii, Frattura ed Integrità Strutturale, 31 (2015) 120-126; DOI: 10.3221/IGF-ESIS.31.09 123 transverse chemical bonds ( ν ch (mol/cm 3 ) ) and variable physical (intermolecular) bonds ( ν ph (mol/cm 3 ) ), and the latter determine the temperature-velocity dependence of the mechanical characteristics:       1 1 2 3 3 3 1 1 29 0.225 10 eff ch r ph g ch r g T T exp T T                          (7) The molecular structure parameter (the statistically average internodal molecular weight ( c M ) of 3D cross-linked systems based on low-molecular-weight polymers with terminal functional groups) was theoretically evaluated in the following paper [11]. However, the authors did not consider the molecular interaction, which as well as the mechanical properties depend, as was noted above, on a variety of factors [12-14]. Therefore, for use in engineering practice of determining the ruptural deformation of the free polymeric binder depending on the amount of ν eff we have summarized the experimental data obtained earlier [7]. It turned out that the nonlinear experimental dependence     0 % b eff f    for various polymeric binders, built on a logarithmic scale [7], is linearized in the coordinates: 0 0 log log | c b b eff M C       (8) where 0 log | 3.1 c b M    corresponds to 0 | 1250% c b M    ; coefficient C = 40; 1 eff c d M    is in accordance with the formula (7). After algebraic transformations we obtain an empirical dependence: 3.1 40 0 10 eff b     (9) M ATERIAL AND M ETHODS reaking strain was measured on a tensile testing machine brand "Instron," at a rate of expansion "."The materials used in the study cross-linked elastomers based on viscous-flow low-molecular rubbers with terminal functional groups – poly(butyl formal sulfide), poly(ester urethane)hydroxide, polydiene epoxy urethane, poly(isoprene– butyl), carboxyl-terminated polybutadiene – cured by three functional agents with antipodal functional groups. Low-molecular rubbers (PDI-3B grade polydiene epoxy urethane with epoxy end groups and SKD-KTR grade carboxyl- terminated polybutadiene) were used as the polymer matrix. 3D cross-linking was performed using EET-1 grade epoxy resin. Mixtures of silica fractions with an average particle size (600 µm, 15 µm, and 1 µm) were used as the filler. The polymeric binder contained dibutyl phthalate as a plasticizer   [ 1 0.3] sw r      . Optimum values of the fraction parameters are listed in Tab. 1, 2 and 3. The selected standard relative strain rate is 1.4·10 -3 c -1 . Fig. 1 presents a generalized dependence of ruptural deformation of different polymer binders (on a logarithmic scale) on the square root of the effective concentration of transverse bonds (on a linear scale). Taking into account the relations (6), by means of the generalized dependence (9) we can determine elongation at break (   0 b mm  ) of the polymeric binder in the free state and hence the ultimate elongation of the three-dimensionally cross- linked filled elastomer (   f b mm  ), which allows us to calculate the energy of its mechanical fracture at uniaxial tension. The Eq. (5), showing the dependence of fracture energy on the parameter / m   , was applied for a PCM based on a low- molecular rubber. Fraction number Particle diameter, µm Pore volume ratio Optimum values of fraction volume ratio Maximum volume filling 1 15 0.386 0.2 0.84 2 600 0.244 0.8 Тable 1 : Parameter values of mixtures of two silica fractions B